The present invention generally relates to coating spray booths and more particularly, to apparatus and methods for measuring coating accumulations in spray booths.
A spray booth is typically provided with cleaning apparatus for removing coating overspray from air within the spray booth. Commonly, the cleaning apparatus utilizes water spray and/or water curtains to extract finely divided coating particles from the air. Examples of such cleaning apparatus are disclosed in U.S. Pat. Nos. 4,096,066; 4,295,866; and 4,475,447. As shown in these patents, a cleaning apparatus utilizing a water curtain typically includes an upper trough disposed above a barrier structure. The upper trough is fed with a supply of water so as to overflow and form a falling water curtain in front of the barrier structure. A lower trough is disposed below the barrier structure and collects the falling water from the upper trough. Although not shown in the above referenced patents, a sump area may be disposed below the lower trough and water in the lower trough may be permitted to overflow into the sump area. In so doing, a second, smaller, water curtain is formed. A baffled air duct is disposed behind the barrier structure and includes an exhaust portion fitted with a fan for drawing air upwardly through the air duct. Water spray nozzles may disposed in the air duct.
During a coating operation, a coating technician stands between a back region of the spray booth and the cleaning apparatus and directs a spray of coating onto an object to be coated, in the direction of the cleaning apparatus. In this manner, overspray is directed toward the water curtain(s). Air (with coating overspray) flows through the water curtain(s) and under the barrier structure and/or under the lower trough and into the air ducts, where the air may be further washed with water from the spray nozzles. The cleaned air is then exhausted from the air duct.
In a spray booth of the type described above, the inventors of the present invention noticed that, after a period of time, coating overspray accumulates in increasing amounts in the back region of the spray booth located behind the coating technician. The inventors have studied this problem and have determined the cause of this overspray in the back region. In connection with this determination, the inventors have developed a method and apparatus for viewing and measuring overspray accumulation in a spray booth. The present invention is directed to this method and apparatus.